I would recommend one of the WD devices, either a Live Hub or a Live Streaming Media Player depending on if you want a hard drive on board or not. I have a WD Live Plus, a WD Live Hub, a Roku XD and am running XBMC on a reasonably powerful PC. I keep all of my media ( near 2000 movies, many TV series and 1000s of CD Rips and concerts) on a file server with 10 drives. All of the products work well for what they do, but the WD Live Hub is by far my favorite for playing media from my home network. It also seems to make sense if you are replacing a Media Device and are just looking to swap it with another one that is pretty much ready to go out of the box. You can use it as simple as you like, or customize the themes / movie sheets etc.
And no, it is not even close to as configurable as XBMC, but it is a lot easier to build, since you don't have to. Out of the box it will play pretty much every Audio and Video format you can throw at it.